1. Field of the Invention
The present invention relates to duct stiffening devices. More particularly the invention relates to a duct stiffening device having a rotatably engagement end allowing for engagement of the device to ducts having angled opposing sidewalls such as transitions, ogee configurations, and offsets.
2. Prior Art
Heating, ventilation, and air conditioning (HVAC) ductwork has often required the need for reinforcement of the sidewalls to prevent sagging, bulging under pressure and from other forces, and buckling. A conventional solution is to brace opposing sidewalls by engaging a rigid support rod and fastening the ends of the rod through an engagement through the respective sidewall.
There are many examples in prior art, which have tried very different approaches with limited success and consequently the art is still lacking and seeking a solution to the shortcomings noted herein. Examples in prior art include U.S. Pat. No. 6,116,833 to Ellis which teaches a reinforcing tie rod for ducts. Each end has a flange which engages into the opposing walls and is secured thereon to provide reinforcement of the duct.
In a different approach U.S. Pat. No. 6,901,969 to Siiter teaches a plug device which can be engaged to the ends of a conduit. The conduit can then be employed to reinforce a duct by aligning the conduit with holes in the duct, and inserting a bolt through the holes and into internally threaded openings provided on the plugs.
U.S. Pat. No. 4,249,578 to Freeman teaches a length adjustable stiffener for fiberboard ducts. The device includes two telescopically mated tubes having laterally extending end flanges for engaging the inner faces of opposite panels of rectangular fiberboard ducts to brace them against sagging and/or bulging caused by air-pressure-difference and/or gravitational forces.
However, despite the different approaches to solving the problems in the art, a common drawback of these and similar devices are that they are limited to square or rectangular cross sectional duct systems. Further, the prior art is only employable on duct systems which are constant in diameter and therefor which do not taper or transition. Conventional stiffening devices and systems employ fixed angle engagement ends/flanges/plugs and are intended to brace sidewalls which are opposed at 180 degrees. Therefor conventional duct stiffening devices fail to provide a means for reinforcement and stiffening of angled or offset ducts, or curved or transitioning ducts or ducts using an offset stiffening member.
As such, there is a continuing unmet need for a duct stiffening device having ends which accommodate uneven opposing positions, any shaped duct, narrowing and widening walls of ducts, and other requirements for duct stiffening. Such a device should employ rotatably engaged ends interfacing with reinforcing members to allow employment with rectangular, round, square, or narrowing or widening angled ductwork, such as ogee transitions, and offsets.
The forgoing examples of related art and limitation related therewith are intended to be illustrative and not exclusive, and they do not imply any limitations on the invention described and claimed herein. Various limitations of the related art will become apparent to those skilled in the art upon a reading and understanding of the specification below and the accompanying drawings.